US6776432B2 - Drawbar adapter for pull-through swivel hitch - Google Patents

Abstract

One embodiment of the invention relates to an adapter assembly for a towing vehicle having a drawbar hitch for connecting a towed implement having a pull-through swivel hitch assembly to the towing vehicle. The adapter assembly includes a drawbar extension member having a horizontal cross pin, a clamp assembly to secure the drawbar extension member to the drawbar, an adapter frame having a hook to engage the cross pin, and a trunnion pin to couple the adapter frame to the swivel hitch assembly.

Description

This application claim the benefit of Provisional Application No. 60/230,027, filed Sep. 5, 2000.

FIELD OF THE INVENTION

The present invention relates generally to a towed implement that is towed and mechanically powered by a towing vehicle. In particular, this invention relates to an adapter assembly carried by the drawbar of a towing vehicle for connection to a towed implement having a pull-through swivel gearbox assembly.

BACKGROUND OF THE INVENTION

Pull type implements have been used in farming operations for decades. For example, the agricultural implement may be a mower designed to cut and process hay or other crops. The implement may also be configured as a forage harvester, hay recovery implement, baler, sprayer, or ground breaking implement. Typically, the implement is towed and powered by a towing vehicle such as a tractor. A power-take-off shaft (PTO) of the tractor typically provides mechanical power to the implement.

The implement is typically connected to the tractor by a pivoting draft tongue. In many implements, a hydraulic swing cylinder interconnects the implement frame and the draft tongue. The hydraulic cylinder controls the pivotal movement of the draft tongue. The pivoting tongue may be positioned so that the implement is directly behind the tractor or to the left or right side of the tractor. As previously indicated, the implement is mechanically powered by the PTO on the tractor. Hydraulic pressure for the implement is provided by the hydraulic system of the towing vehicle.

There are two common methods of attaching the draft tongue of the implement to the towing vehicle. One is to connect the draft tongue directly to the drawbar of the towing vehicle. A simple hitch pin can be used to drop through a hole in the draft tongue and into a hole in the towing vehicle drawbar. The implement tongue may also have a ball joint to allow freedom of rotation about the vertical (yaw) axis, the horizontal (pitch) axis and the fore and aft (roll) axis or the hitch pin joint may be loose enough to allow the rotation needed.

The other method of attaching the draft tongue of an implement to a towing vehicle is to use a swivel hitch on the implement. A swivel hitch involves a set of gearboxes, one above the other, with a connecting drive shaft between them. The gearboxes can swivel relative to each other. The relative swivelling motion becomes the vertical (yaw) axis of rotation.

Typically, the swivel hitch has a frame member that pivots on the same yaw axis as the swivel gearboxes and connects to the three point hitch assembly on the towing vehicle. The upper gearbox Is fixed to the draft tongue. The lower gearbox and swivel hitch frame pivot relative to the upper gearbox and follow the tractor as it turns.

The advantage of the swivel hitch over the standard pinned connection is that the yaw axis is further behind the towing vehicle, allowing for much sharper turns. With a pinned drawbar connection, the hitch point is close to the tractor. Thus the tractor can not turn sharply because the rear tire will engage the draft tongue of the implement.

There are two types of swivel hitch designs common in the industry. One is a pull-through design wherein the gearboxes are connected structurally to transmit load from the swivel hitch frame to the draft tongue. The other design involves a swivel hitch frame that is connected structurally to the draft tongue so that the implement does not transmit any structural load through the gearboxes.

The advantage of the pull-through design is that it is a much simpler design and does not require a device to guide the lower gearbox to follow the tractor, since the swivel hitch frame is connected directly to the lower gearbox.

Preferably a trunnion assembly is also located adjacent the gearbox assembly on the draft tongue of the implement. The trunnion assembly allows the implement to rotate or tilt about the fore and aft longitudinal roll axis.

One major drawback to any swivel hitch is that many tractors are not equipped with a three-point hitch system. Also, some operators find the lower links of a three-point hitch cumbersome to hook up.

For these reasons, a mechanism to adapt a tractor drawbar for connection to the swivel hitch of a pivoting draft tongue is desired.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a drawbar hitch adapter assembly that allows a mechanically powered implement having a pull-through gearbox assembly to connect to the drawbar of a tractor.

Thus, one embodiment of the invention includes an adapter assembly for a towing vehicle having a drawbar hitch for connecting a towed implement having a pull-through swivel gearbox assembly to the towing vehicle. The adapter assembly includes a drawbar extension portion having a horizontal cross pin, a clamp assembly to secure the drawbar extension portion to the drawbar, an adapter frame portion having an open hook to engage the cross pin and a trunnion assembly to couple the adapter frame portion to the swivel hitch assembly.

The adapter assembly may further include a pivotally mounted pawl on the adapter frame to rotate from an open position to a closed position to secure the open hook in the closed position.

The adapter assembly may also include a flat vertical surface on the hook for contact by the cross pin when the tow vehicle is moved into a hitching position with the towed implement so as to indicate an alignment position of the cross pin relative to the hook.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a top plan view representing a towing vehicle such as a tractor and a towed implement having a pivoting draft tongue incorporating the present invention.

FIG. 2 is a side view of the adapter assembly of the present invention mounted to the drawbar hitch of a towing vehicle and the pull-through gearbox assembly on the pivoting draft tongue of the towed implement of FIG.1.

FIG. 3 is an exploded perspective view of the adapter assembly of FIG.2.

FIG. 4 is another perspective view of the adapter assembly that is similar to FIG.3 and shows additional detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a towedagricultural implement10 is shown connected to atowing vehicle12, such as a tractor. Theimplement10 is thereby towed generally behind thetowing vehicle12 during operation and transport. FIG. 1 shows that thetowing vehicle12 can tow theimplement10 in an extended straight-line position and also in an angled position, as is the situation for example when a tight turn at the end of a field is being performed.

The towedimplement10 includes a pair ofground support wheels14 and a pivoting forward extendingdraft tongue16. The towedimplement10 includes a driven, articulated power shaft, which transmits mechanical drive from thetowing vehicle12 to the working parts of theimplement10.

In a pull through swivel hitch type of implement, the power transmitting mechanism includes agearbox assembly20. The gearbox assembly includes anupper gearbox22 fixed to and rotating with the pivotal draft tongue. Alower gearbox24 is connected to the upper gearbox by a driveshaft but can pivot relative to the upper gearbox and the draft tongue. Atrunnion assembly26 is provided adjacent the lower gearbox.

To provide mechanical drive for theimplement10, thetowing vehicle12 is equipped in its rear region with a known power take-off (PTO) stub shaft28 which is connected to the articulated power shaft of the implement.

The forward end of thepivoting draft tongue16 is coupled to thetowing vehicle12 by a coupling mechanism. Usually, thetowing vehicle12 is an agricultural tractor with a three point hitch assembly. A three point hitch assembly includes lower draft arms and an upper center arm, which can be moved vertically, in a well known manner, in order to raise or lower an attached tool or implement. The three-point hitch arrangement however is not employed with this invention and therefore details of its construction are not included in the drawings.

The connecting and towing mechanism of the present invention is a fixed drawbar hitch, shown generally at30. The connecting assembly for towing the implement from thedrawbar hitch30 according to the present invention is the drawbar adapter assembly shown generally at32.

As shown in FIG. 2, the drawbar adapter assembly32 is generally a pin and hook system. The system includes twoframe portions40 and42. Afirst frame portion40 of the adapter assembly32 is clamped to thedrawbar hitch30 of the tractor. Thesecond frame portion42 of the drawbar adapter assembly32 is attached to thepivoting draft tongue16 of the pull through implement at thetrunnion assembly26 adjacentlower gearbox24. Thetrunnion assembly26 provides for roll axis freedom for the towed implement.

As best seen in FIGS. 3 and 4, thefirst frame portion40 of the adapter assembly32 includes adrawbar extension member44 having aproximal end46 and a bifurcateddistal end48. Theproximal end46 is configured to fit over the top of thedrawbar hitch30. The distal end of the drawbar extension member includes anopen yoke50 having a pair ofopposed holes52. The holes may be provided with sleeves orbearings54. Aremovable cross pin60 is positioned through the pair ofholes52 and horizontally across the yoke in thedrawbar extension member44. Thecross pin60 is secured in the yoke by a known securing mechanism, such as at least one smaller pin (not shown) through both thecross pin60 and sleeve orbearing54. The securing mechanism allows thecross pin60 to be removed and replaced as needed.

Thefirst frame portion40 further includes a clamping assembly62 including abottom bracket member64. Thedrawbar hitch30 is clamped between thedrawbar extension member44 and thebottom bracket member64 with clamp bolts66 (shown in FIG.2). Thebottom bracket member64 is preferably formed with alongitudinal channel68 having two beveled or sloped surfaces70. The beveled surfaces70 contact two bottom corners of the drawbar and provide adjustibility to fit different size drawbars.

Adrawbar hitch pin72 is vertically inserted from the top or bottom of thefirst frame portion40 so as to pass through a suitable hole in thedrawbar extension member44, through the hole in thedrawbar hitch30 and throughout a matching hole in thebottom bracket member64. A cotter pin is used to secure thedrawbar hitch pin72 in place. Thedrawbar hitch pin72 prevents thedrawbar extension member44 from being pulled longitudinally off thedrawbar hitch30. Set screws74 (only one shown) through the opposite sides of thedrawbar extension member44 are used to resist rotation of thefirst frame portion40 about the vertical axis of thedrawbar hitch30 should the clampbolts66 loosen.

Thesecond frame portion42 for the draft tongue of the implement includes aframe body80 and a fixed downwardopen hook82. A pivotingpawl84 is positioned adjacent and opposite the open hook on theframe body80. Thepawl84 pivots on a pawl pivot pin86 (shown in FIG. 2) and remains open under the pawl's own weight during hookup. An insertable locking pin88 (shown in FIG. 2) is provided to secure the pawl in the closed position.

When towingvehicle12 is hooked up to the implement10, thehorizontal cross-pin60 in the tractordrawbar extension member44 is positioned under the fixed downwardopen hook82 of the implementsecond frame portion42. The operator uses a mechanism on the implement, such as an adjustable jack, to lower the implement. Theopen hook82 has a flatvertical surface90 adjacent and below the open portion of the hook. The flatvertical surface90 and chamfered edges on thehook82 help guide the hook down onto the cross-pin60 when the twoframe portions40 and42 are not in direct alignment.

A method for connecting a towed implement having a pull-through swivelhitch gearbox assembly20 to a towing vehicle having adrawbar hitch30 will now be described. Thedrawbar extension member44 having ahorizontal cross pin60 is positioned on the drawbar of the towing vehicle. The clamping assembly62 including thebottom bracket member64, theclamp bolts66 and theset screws74 are used to secure thedrawbar extension member44 to thedrawbar hitch30. Thedrawbar hitch pin72 is also inserted through thedrawbar extension member44, the drawbar and thebottom bracket member64. Thesecond frame portion42 having a downwardopen hook82 is positioned on thedraft tongue16 of the implement and coupled to the swivelhitch gearbox assembly20. The implement10 is then lowered to engage the downwardopen hook82 onto engagement with thecross pin60.

The pivotally mountedpawl84 is then manually rotated into a closed position to prevent the fixedopen hook82 from disengaging from thecross pin60. The pawl is retained in this position with a securing mechanism such as a locking pin, for example a hairpin cotter pin.

The drawings, specific examples, and particular embodiments serve the purpose of illustration only. The materials and configurations shown and described may differ depending on the chosen performance characteristics and physical characteristics of the equipment. For example, the type of harvesting equipment may differ. The systems shown and described are not limited to the precise details and conditions disclosed. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiments without departing from the spirit of the invention as expressed in the appended claims.

Claims (11)

What is claimed is:

1. A drawbar adapter assembly for a towing vehicle having a drawbar hitch for connecting a towed implement having a pull-through swivel hitch gearbox assembly to the towing vehicle, the adapter assembly, comprising:

a first frame portion including a drawbar extension member having a proximal end and a distal end defining an open yoke;

a horizontal cross pin spanning the open yoke;

a clamp assembly to secure the drawbar extension member to the drawbar hitch;

a second frame portion having an open downward hook for engagement with the cross pin; and

a trunnion assembly to couple the second frame portion to the swivel hitch gearbox assembly,

wherein the clamp assembly comprises a bottom bracket member positioned under the drawbar hitch and is securable to the drawbar extension member to provide a clamping load on the drawbar hitch so as to capture the drawbar hitch between the bottom bracket member and the drawbar extension member and wherein the bottom bracket member includes a channel cross-section having two beveled sides edges to engage the drawbar hitch for adjustable fit of the drawbar hitch.

2. The adapter assembly ofclaim 1 further comprising a pawl pivotally mounted on the second frame portion opposite the open hook so as to rotate from an open position to a closed position to secure the hook on the engaged cross pin.

3. The adapter assembly ofclaim 2 further comprising means for locking the pawl in the closed position.

4. The adapter assembly ofclaim 1 further comprising means for guiding the open hook into alignment with the cross pin when the towing vehicle is moved into an abutting position with the towed implement.

5. The adapter assembly ofclaim 4 wherein the means for guiding is a flat vertical surface adjacent the open hook which guides the hook onto the cross pin as the second frame portion of the implement is lowered onto the cross pin of the drawbar extension portion.

6. In a towed implement having a pull-through swivel hitch gearbox assembly for connection to a towing vehicle having a drawbar hitch, a drawbar adapter assembly for the towed implement comprising:

a drawbar extension member having a distal end with an open yoke and a horizontal cross pin;

means for securing the drawbar extension member to the drawbar hitch;

an adapter frame portion having an open downward hook to engage the cross pin; and

a trunnion assembly to couple the adapter frame portion to the swivel hitch gearbox assembly and to allow rotation about a roll axis, wherein the trunnion assembly is disposed relative to the open downward hook such that torque about the roll axis is dissipated by the trunnion assembly prior to acting on the open downward hook,

wherein the means for securing comprises a bottom bracket member positioned under the drawbar hitch and is securable to the drawbar extension member to provide a clamping load on the drawbar hitch so as to capture the drawbar hitch between the bottom bracket member and the drawbar extension member.

7. The towed implement ofclaim 6 further comprising a pawl pivotally mounted on the adapter frame portion opposite the open hook to rotate from an open position to a closed position to retain the hook on the engaged cross pin.

8. The towed implement ofclaim 7 further comprising means for locking the pawl in the closed position.

9. The towed implement ofclaim 6 further comprising means for guiding the open hook into alignment with the cross pin when the towing vehicle is moved into an abutting position with the towed implement.

10. The towed implement ofclaim 9 wherein the means for guiding is a flat vertical surface on the open hook which guides the hook onto the cross pin as the adapter frame portion of the implement is lowered onto the cross pin of the drawbar extension portion.

11. The towed implement ofclaim 6, further comprising a draft tongue, wherein the swivel hitch gearbox assembly includes an upper gearbox affixed to the draft tongue and a lower gearbox pivotally connected to the upper gearbox, and the means for securing is affixed to the lower gearbox, whereby a pulling load is transmitted from the drawbar hitch through the upper and lower gearboxes to the draft tongue.

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